1. Technological Field
This technical disclosure pertains generally to camera autofocus systems, and more particularly to an area selection mechanism to facilitate autofocusing on moving objects within the camera field of view.
2. Background Discussion
An autofocus (AF) mechanism in a camera device adjusts the lens of the camera to proper focus at a given depth on the subject being captured by the camera. For instance, pressing the shutter release with a first level of pressure engages the autofocus mechanism, with a higher second level of pressure activating image capture.
In a typical scene, however, the different elements of the scene are at different depths from the camera, and thus optimum focus depends on what depth the subject is at within the field of view. Cameras often provide one or more mechanisms for single-shot autofocus. For example an AF area selection may comprise a specific area of the image upon which to optimize focus, for example a focus box fixedly retained in the center of the field of view. For dynamic scenes having one or more moving objects, various continuous AF mechanisms have been developed which attempt to lock onto a subject and remain focused on them, for instance locking on a specific area of a known object, for example the face of a human object. It is understood that a number of known object types exist for which parameters, techniques and/or classification methods are available to allow estimating spatial extent of the known object and specific areas of this known object.
However, these AF mechanisms provide less than desirable results when capturing images (video) of intensive and/or unpredictably moving subjects.
Accordingly, an improved mechanism is needed for performing area selection in the driving of the autofocus process within a still or video camera. The present disclosure fulfills that need while overcoming many shortcomings of prior approaches.